The microstructure of Ti/Au contacts on n-type GaN annealed in nitrogen

Ti(40 nm)/Au(120 nm) contacts have been prepared on n-GaN/sapphire. The contacts were annealed from 400 degrees C to 900 degrees C for 10 min in nitrogen, respectively. The interaction between the contact metallization and the GaN epitaxial layer (on sapphire) was investigated by electron microscopy and X-ray diffraction. It was found that for an annealing at a temperature equal or higher than 700 degrees C, the gold diffused through Ti layer and Au-rich grains were formed under this Ti layer. Between the Au-rich grains and the n-type GaN layer a new Ti-rich thin layer was identified by XTEM. High resolution images and X-ray data showed that it's TiN(0.26) that was formed at the metal/semiconductor interface. FESEM investigations showed that Ti/Au contacts annealed in nitrogen still have a very smooth surface morphology. (C) 2011 Elsevier B.V. All rights reserved.